Thermally actuated snap action device



' Nov. 16, 1965 H. VOORMAN, JR 3,218,415

THERMALLY ACTUATED SNAP ACTION DEVICE Filed March 7, 1963 ATTORNEYSUnited States Patent 3,218,415 THERMALLY ACTUATED SNAP ACTION DEVICEHenry Voorman, In, Midland Park, N.J., assignor to Tung-Sol ElectricInc., a corporation of Delaware Filed Mar. 7, 1963, Ser. No. 264,479 6Claims. (Cl. 200-122) This application is a continuation-in-part ofapplication Serial No. 77,155, filed December 20, 1960, now abandoned.

The present invention relates to snap action devices of the general typeof that of Schmidinger Patent No. 2,615,106 dated October 21, 1952 andreissue thereof No. 24,023, dated June 14, 1955 and comprises animproved flasher which is readily stabilized for current and voltagefluctuations, lends itself to mass production in that adjustments arenot too critical, requires few parts and has improved resistance toshock and vibration.

As in the patented device, which has had wide commercial use for controlof automobile turn signals, the new flasher comprises a vane ofresilient conductive material having an inherent deformation therein andan expansible pull ribbon or wire secured at its ends under tension tospaced points on the periphery of the vane, the pull ribbon whenexpanded as a result of current therethrough permitting the vane to snaptoward the configuration into which it is constrained by the inherentdeformation. In the patented flasher the pull ribbon is disposedgenerally parallel to the axis about which the vane is deformed, and itslength relative to the vane dimensions is such that when fully expandedno extended length thereof contacts the vane surface. In the flasher ofthe present invention the pull means is disposed at an angle to thedeformation and when expanded a substantial length of the pull ribbonengages the surface of the vane and is rapidly cooled thereby. Rapidcooling permits operation at lower temperatures where the cooling rateis ordinarily too low for efficient operation. Operation at lowertemperatures minimizes variations in ratio and rate of flashing withchange in supply voltage as will be apparent as the descriptionproceeds.

Briefly, the new flasher comprises a vane of resilient conductingmaterial given an inherent curvature about one axis, as by creasing, anda tensioned pull ribbon extending diagonally across the vane on theconvex side of the inherent curvature thereof. A fixed contact isdisposed in a position to be engaged under pressure, when the pull stripis cold, by a contact mounted at the center of the pull strip. The vaneis supported at a location adjacent an edge thereof. Preferably thesupport means extends beyond the location of attachment to the vane andis shaped to engage the vane when it snaps to contact open position andthereby enhance noise.

For a better understanding of the invention and of various embodimentsthereof reference may be had to the accompanying drawings of which:

FIG. 1 is a front view with the cover in section of a flasher embodyingthe invention;

FIG. 2 is a view of the device of FIG. 1 taken at right angles thereto;

FIG. 3 is a view similar to FIG. 2 but showing the position of the partswhen the pull ribon is expanded;

FIG. 4 is a top plan view of the new flasher in the condition of FIG. 3;

FIGS. 5 and 6 are views of alternative constructions of vane suitablefor use in the flasher of the invention;

FIG. 7 is a graph explanatory of the operation and of the advantages ofthe new flasher.

As shown in the drawings the flasher comprises an insulating base 2which may be of any suitable molded plastic material having terminals 4and 6 extending thereice through. Terminal 4, above the base 2, extendsupwardly to provide the support 8 for the snap vane 10. The vane is ofrectangular shape and is longitudinally creased as indicated at 12. Apull strip 14 on the normally convex side of the vane is secured todiagonally opposite corners 16 and 18 of the vane under such tension asto spring the vane against the curvature introduced by the crease 12.The pull strip 14 need not be exactly diagonal but may be connectedslightly off from one corner 16. The corners 16 and 18 are preferablybent to provide a fulcrum over which the pull strip exerts a bendingforce on the vane and also to provide means for adjustment of thetension in the pull strip.

A contact 20 is welded to the center of the pull strip and this contact,in the cold position of the pull strip illustrated in FIGS. 1 and 2,engages under pressure a contact 22 mounted on the upper end of theupwardly extending portion 24 of terminal 6. Support 8, as shown best inFIG. 1, is welded to the vane 10 adjacent the lower edge thereof andslightly further from the corner 16 than from the other lower corner ofthe vane. Above the point of attachment of the support 8 to the vane 10the support is bent outwardly and then inwardly to provide a stop 26 forthe upper part of the vane 10. The stop 26, which is engaged by the vanewhen the vane snaps toward its constrained position upon expansion ofthe pull strip (see FIG. 3), enhances the noise of the operation of theflasher.

The vane of FIG. 5 differs from that of FIGS. 1 and 3 only in that theinitial constraint along the central longitudinal section is provided byribs or bosses 28 which are stamped or otherwise formed in the vane. Therib or ribs could be continuous for the length of the vane as in thecase of the crease 12 of the embodiment of FIG. 1, or could beinterrupted at the center of the vane, as for example, at an aperture 30in the central portion of the vane. As will be apparent from thedrawing, the ribbon 14 in the embodiment of the invention illustrated inFIGS. 1 and 5 is not exactly diagonally disposed being connected at thelower right hand edge of the vane slightly above the corner of the vane.Also, in these embodiments the ear to which the pull ribbon is attachedat the lower right corner is somewhat larger than the ear at the upperleft corner of the vane. The reason for the location of the lower righthand end of the ribbon and of the difference in magnitude of the earswill become apparent as the description proceeds.

The vane construction illustrated in FIG. 6 represents the presentlypreferred embodiment of the invention. In this construction, the ribbon14 is connected diagonally across the vane, the ears to which the ribbonis attached are substantially of the same size, and diagonal creases 36and 37 which are convex toward the ribbon are formed in the vaneextending from a short edge toward the ribbon. The crease 36 isrelatively sharper than the crease 37. In addition to the initialconstraint introduced by the crease 12, two ribs or bosses 34 and 35,convex toward the ribbon, are formed in the vane along the diagonalopposite to that over which the pull ribbon is disposed. These embossesor ribs 34 and 35 are so formed as not to introduce any curvature intothe vane, but are provided solely to stiffen the blade and raise theresonance frequency for purposes of better quality of the noisegenerated during operation of the flasher. Also to increase the qualityand level of the sound an additional crease 32 convex to the ribbon sideof the vane is formed in the upper half of the vane. The crease 32extends from the upper edge of the vane toward the central hole 30 at anangle of substantially to the diagonal over which extends the pullribbon. The crease 32 provides a backward bias to increase the storedenergy by requiring an 9 increase in ribbon tension. It also stitfensthe blade, and raises the resonance frequency.

Irrespective of which of the blades of FIGS. 1, and 6 is incorporated inthe flasher, the operation of the device is in general like that of theaforementioned Schmidinger reissure patent in that when a circuitincluding a source of energy, such as a car carried battery, and a lampload or other device to be intermittently operated is connected acrossterminals 4 and 6 current flows through the vane and pull strip andclosed contacts 20 and 22. This current heats the pull strip and causesit to expand. Upon expansion of the pull strip the vane snaps into theposition shown in FIGS. 3 and 4 in which position the contacts are open.The pull strip thereupon cools and the vane snaps back into the contactclosing position of FIGS. 1 and 2. The cycle then repeats.

For flashers for automobile turn signals the industry prefers a ratio ofon time to full cycle time of about 50 percent and also requires thatthe ratio and the rate of flashing remain fairly constant over a rangeof variation of supply voltage. With series type flashers in generalwhen the battery voltage increases the on period decreases andconversely when the current decreases the on period increases. The offperiod remains constant. The operate and reset temperatures, andtherefore the heating and cooling times, for any given flasher may byadjusted by adjustment of the initial tension of the pull ribbon, and byadjustment of the spacing of the contacts. If a lower operate and resettemperature can be employed, the on period will not vary greatly withchange in operating voltag because at such lower temperatures theheating curves for the extremes of current are steeper and closertogether. However, with the usual series type flasher at lower operateand reset temperature, the cooling rate is such that the off period isrelatively long and hence it is diflicult to maintain the desired 50percent ratio.

In the flasher of the invention, a faster cooling rate is obtained by soconstructing the vane and by so adjusting the vane that during the offperiod the ribbon contacts the surface of the vane over one quandrant ofthe vane and therefore cools more rapidly by conduction to the vane. Inorder to make the ribbon thus contact the vane during the coolingperiod, the following conditions are required. The relationship of thepoints on the vane at which the ribbon i attached to the surface of thevane must lie relatively in front of the surface during the on portionof the cycle and behind the surface during the off cycle. This implies areversal of curvature from concave to convex of a portion of the vanelying under the ribbon. When the ribbon is parallel to the majordeformation of the blade, as for example, in the device illustrated inthe said Schmidinger patent, or is perpen dicular to the maindeformation, such reversal of curvature does not occur. With the ribbonpositioned at an angle to the main deformation it becomes possible toadjust the device for proper contact of the ribbon with the vane duringthe off cycle. In the embodiment of the invention illustrated in FIGS. 1and 5., the desired contact of ribbon to vane is obtained by positioningthe lower end of the ribbon slightly away from the corner of the vaneand by bending a larger ear at that corner than at the upper left cornerof the vane. With this construction the ribbon tension can be soadjusted as to insure good contact of the ribbon with the vane duringthe off cycle. In the embodiment of FIG. 6, the same result i obtainedby the provision of the diagonal creases 36 and 37. The crease 37 may beomitted but is of use in mass production as an additional means ofadjustment. The crease 36 is relatively sharper than the crease 37 andis the prime means of adjustment to insure ribbon and vane contacts inthe off period. Because of the ease with which the vane of theconstruction of FIG. 6 can be adjusted for the desired ribbon and vanecontact, it represents the preferred embodiment of the invention and onewhich is now in wide commercial use.

That the ratio can be maintained substantially constant when the operatetemperature of the flasher is relatively low and if the cooling rateduring the off cycle is relatively rapid will become apparent from thefollowing description of FIG. 7. In FIG. 7 the curve A representsqualitatively the average cooling rate for flasher devices of thegeneral type of the said Schmidinger patent and reissue. The steepercurve B of FIG. 7 similarly represents the cooling rate of the device ofthe present invention. Curve C of FIG. 7 represents the heating rate ofa pull strip of specific dimensions at an upper limit of appliedvoltage, say 14 volts, and curve D of FIG. 7 represents the heating ratefor the same dimensioned pull strip at the lower limit of the appliedvoltage, say 11 volts. It will be apparent from the comparison of thecurves C and D that the lower the operate temperature the less thedifference will be in rate of flashing with change in operating voltage.For example, if the operate temperature is T that is if the device snapsto contact open position at temperature T then when the circuit is firstclosed if the supply voltage is 11 volts the flasher will snap tocontact open position in a period that is longer by an interval At thanwhen the supply voltage is 14 volts.

At a higher operate temperature, T there is a greater difference intime, At required for the flasher to snap to contact open position at 11volts than at 14 volts. Thus the lower the operate temperature the lessefifect variations in supply voltage have upon the operation of theflasher. Without the more rapid cooling of the pull ribbon, provided byapplicants construction of flasher, the operate temperature for thedesired 50 percent ratio must be that midway between zero and maximumtemperature rise. This is because this midway temperature is the onlytemperature at which the heating and cooling rates of the ribbon areequal. Above this midway temperature the ratio will be over 50 percent,that is the device will be long on and below this midway temperature theratio will be under 50 percent, or the device short on. When the coolingrate is increased in ac cordance with the invention the desired 50percent ratio occurs at a temperature lower than the midway temperatureand consequently an operate temperature may be selected in the lowtemperature range where difference in operating voltage has a relativelysmall effect upon the rate of flashing.

The invention has now been described with reference to severalembodiments thereof. Obviously, changes in details of construction couldbe made without departing from the spirit of the invention or the scopeof the accompanying claims.

What is claimed is:

1. A snap action device comprising a rectangular vane of conductiveresilient material having a linear deformation therein, a pull strip foralternately snapping the vane position wherein it is buckled about anaxis angularly disposed to said deformation and a second position towardwhich it is biased by said deformation, said alternate snapping inresponse to the expansion and contraction of the pull strip caused byheating and cooling of the pull strip in repetitive cycles, said pullstrip overlying the convex side of the vane at an angle to saiddeformation and secured at its ends under tension to the vane adjacentdiagonally disposed corners thereof, said pull strip in said secondposition being in heat conductive engagement with the surface of thevane from one point of attachment to the vane to substantially thecenter of the vane to employ the vane as a heat sink for cooling thepull strip to decrease the length of time necessary for the pull stripto contract and snap the vane into said first position, means forheating said pull strip when the vane is in said first position andmeans for supporting said vane.

2. The snap action device according to claim 1 including stiffening ribsdisposed along the diameter of the vane opposite to that over which thepull strip is disposed for increasing the resonant frequency of thedevice.

3. The snap action device according to claim 1 wherein said vane isprovided with a crease, convex toward the pull strip and extending froma shorter side edge toward the diagonal of the vane over which the pullstrip is disposed, said crease tending to maintain the pull strip andvane in contact when the pull strip is expanded.

4. The snap action device according to claim 1 wherein said vane iscentrally apertured and is provided with a crease, convex toward thepull strip and extending from a longer side edge toward said apertureand substantially perpendicular to the diagonal over which the pullstrip is disposed.

5. In a flasher of the type which has a resilient rectangular vane Witha biasing linear deformation therein and has an actuating pull stripattached to the vane adjacent two diametrically opposed corners of thevane so that when the pull strip is cold it holds the vane constrainedin a first configuration in which the vane is buckled about an axiswhich is angularly disposed to the linear deformation and when the pullstrip is heated sufficiently with respect to the vane it allows the vaneto assume a second configuration towards which the vane is biased by thelinear deformation, the improvement which comprises said lineardeformation and said axis both being oriented at an angle to said pullstrip and the vane being so contoured as to be in heat conductingcontact with the pull strip from one end of the pull strip tosubstantially the middle of the pull strip when the vane is in itssecond configuration and to be out of contact with the rest of the pullstrip in said second configuration.

6. A flasher comprising a resilient vane with a biasing lineardeformation therein and an actuating pull strip attached to the vane andoperative when it is cold to hold the vane constrained in a firstconfiguration in which the vane is buckled about an axis which isangularly disposed to the linear deformation and when it is heatedsufficiently with respect to the vane to allow the vane to assume asecond configuration towards which the vane is biased by the lineardeformation, said pull strip overlying the vane at an acute angle tosaid linear deformation and at an acute angle to said axis, and the vanebeing so contoured in said second configuration as to come in heatconducting contact with the pull strip from one end of the pull strip tosubstantially the middle of the pull strip and to be out of contact withthe rest of the pull strip in said second configuration.

References Cited by the Examiner UNITED STATES PATENTS 2,254,687 9/1941Koci 200122 2,615,106 10/1952 Schmidinger 200-122 2,712,045 6/1955 Welsh200122 2,861,149 11/1958 Hollis et al. 200122 3,019,318 1/1962 Welsh200122 BERNARD A. GILHEANY, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 218,415 November 16 1961 Henry Voorman, Jr.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 56, after "vane" insert back and forth between a firstSigned and sealed this 27th day of September 1966.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AttestingOfficer

1. A SNAP ACTION DEVICE COMPRISING A RECTANGULAR VANE OF CONDUCTIVERESILIENT MATERIAL HAVING A LINEAR DEFORMATION THEREIN, A PULL STRIP FORALTERNATELY SNAPPING THE VANE POSITION WHEREIN IT IS BUCKLED ABOUT ANAXIS ANGULARLY DISPOSED TO SAID DEFORMATION AND A SECOND POSITION TOWARDWHICH IT IS BIASED BY SAID DEFORMATION, SAID ALTERNATE SNAPPING INRESPONSE TO THE EXPANSION AND CONTRACTION OF THE PULL STRIP CAUSED BYHEATING AND COOLING OF THE PULL STRIP IN REPETITIVE CYCLES, SAID PULLSTRIP OVERLYING THE CONVEX SIDE OF THE VANE AT AN ANGLE TO SAIDDEFORMATION AND SECURED AT ITS ENDS UNDER TENSION TO THE VANE ADJACENTDIAGONALLY DISPOSED CORNERS THEREOF, SAID PULL STRIP IN SAID SECONDPOSITION BEING IN HEAT CONDUCTIVE ENGAGEMENT WITH THE SURFACE OF THEVANE FROM ONE POINT OF ATTACHMENT TO THE VANE TO SUBSTANTIALLY THECENTER OF THE VANE OF EMPLOY THE VANE AS A HEAT SINK FOR COOLING THEPULL STRIP TO DECREASE THE LENGTH OF TIME NECESSARY FOR THE PULL STRIPTO CONTRACT AND SNAP THE VANE INTO SAID FIRST POSITION, MEANS FORHEATING SAID PULL STRIP WHEN THE VANE IS IN SAID FIRST POSITION ANDMEANS FOR SUPPORTING SAID VANE.